Oxidation of propylene in the presence of acetic acid catalyzed by a palladium catalyst to produce allyl acetate is known. The process includes a reaction (acetoxylation) of propylene with oxygen and acetic acid to form a mixture comprising allyl acetate, propylene, oxygen, acetic acid, water, carbon dioxide, and possibly other inert gases. The reaction mixture is typically separated into a gas stream comprising propylene, oxygen, acetic acid, water, and carbon dioxide, and a liquid stream comprising allyl acetate, acetic acid, and water. Allyl acetate can be separated from the liquid stream. At least a portion of the acetic acid and water separated from the liquid stream is recycled to the acetoxylation reaction.
In addition to allyl acetate, the reaction generally also gives carbon dioxide, allyl diacetate, and possibly acrolein and propionaldehyde. The heat of reaction for the formation of allyl acetate from propylene, acetic acid, and oxygen is about −37.9 kcal/mole. As the reaction is highly exothermic, generally multitubular reactors are used. For example, U.S. Pat. No. 3,970,713 teaches a multitubular reactor containing reactor tubes having a length of from 4 to 8 meters and an internal diameter of from 20 to 50 mm. In a typical mulitubular reactor, the catalyst is arranged in the reactor tubes. A heat carrier fluid circulates externally around the reactor tubes to remove the heat generated by the reaction. Mulitubular reactors are suitable for those reactions with a large heat of reaction as well as reactions that are extremely temperature-sensitive. A mulitubular reactor is often called an “isothermal reactor” because of its relatively uniform temperature through the reactor. Usually, the temperature variation through a multitubular reactor is small, generally less than 20° C.
The disadvantage of a multitubular reactor is its high equipment cost. In addition, it can be time consuming to load and unload hundreds, often thousands, of reactor tubes. It is particularly difficult to remove used catalyst from the reactor tubes when the catalyst in the tubes has agglomerated or fused.